Even with five siblings living overseas, April Murphy doesn't worry too much about trying to stay in touch.

She's got Skype, an Internet-based phone service, and so does her family. Any calls to another Skype user are free, while ringing up a cell phone or landline costs only a few cents per minute.

For the most part, Murphy swears by the system and said if she could, she would trade in her landline and rely solely on Skype and her cell phone.

"If I didn't have to have a landline for business, I would probably get rid of it, just because between Skype and our cell phone, I can't imagine having a real reason to need it," said Murphy, who lives in Mountainview, Calif.

Over the next three years, the Telecommunications Industry Association predicts the use of online phone services, or Voice over Internet Protocol, or VoIP, will grow 20 percent annually within the United States. That would bring the number of VoIP users nationwide to about 33.2 million in 2011, compared to 15.9 million users in 2007, according to the TIA's 2008 Market Review and Forecast.

While Skype advertises itself as more of a supplement to traditional phone services, other VoIP providers believe the Internet is positioned to replace the landline because service is cheaper and the Web can provide unique calling features unavailable through a regular telephone network.

"Really, it seems that whether people like it or not, the future is being driven by technology," said Mary Grikas, executive director of device development at Vonage, one of the nation's largest VoIP providers. "We're getting people hooked on digital phone service, and I do feel that will continue to grow over time."

Said Grant Seiffert, TIA president: "Eventually VoIP will replace the old Legacy network. It's just a matter of time."

But customers and consumers do have concerns with the technology, which works by converting a person's voice into digital data that can be sent over the Web. Unlike a landline, VoIP providers cannot automatically link a person's address with their phone number during an emergency 911 call. Users must manually submit a form telling the location of their VoIP phone.

Also, during a power outage, the technology won't work unless a person has backup power for their computer (which most VoIP providers offer for a minimal price). In addition, only people with a high-speed or a broadband Internet connection can make calls using VoIP, and, sometimes, connections can suffer.

"There are times when I go to pick up the phone and I just can't dial out and it cuts me off," said Melanie Sharp, an Internet phone user and former Utah resident living in Sunnyvale, Calif. "It's not as smooth and reliable as a landline, but most of the time, that inconvenience is worth it."